Footwear outsole

ABSTRACT

An outsole ( 2 ) for footwear ( 1 ) comprises at least one protrusion ( 4 ) having a portion ( 8 ) configured for supporting the footwear against a ground surface (S). A traction-enhancing element ( 6 ) is connected to the protrusion ( 4 ) and selectively insertable between said portion ( 8 ) and the ground surface (S). The traction-enhancing element is attached to at least a portion of the protrusion and configured for bending between a first position and a second position; wherein the traction-enhancing element in the second position is between said portion and the ground surface. The movement of the traction-enhancing element between the first position and the second position is effected by a movement of the footwear predominantly along the ground surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Norwegian patent application No.20120984, filed on Sep. 3, 2012, the disclosure of which including thespecification, the drawings, and the claims is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

This invention relates to traction surfaces. More specifically, theinvention concerns a device for controlling the traction of a footwearoutsole.

BACKGROUND OF THE INVENTION

There are numerous examples of means and methods of improving thetraction of footwear, in order to reduce the hazards associated withwalking on sloping and/or slippery surfaces.

The state of the art includes U.S. Pat. No. 4,160,331 A, describing ashoe having an outsole with a gripping surface. The gripping surface isapplied to the outsole in separated, discrete bands within channels inthe outsole and comprises a mixture of grit, such as silicon carbide,and an adhesive. The gripping surface is intended to prevent or curtailslipping by the wearer on smooth surfaces, such as ice or snow.

The state of the art also includes US 2011/0192054 A1, describing a boothaving an outsole with embedded traction enhancing studs. Each stud ispartially embedded in the carrier portion of the outsole and projectsfrom the carrier portion.

The state of the art also includes CA 2 535 426 A1, describing anantiskid attachment for footwear. The attachment comprises of amultitude of skid-resisting elements positioned between the shoe outsoleand the surface, and flexible linkage used to ensure appropriatepositioning of the elements when walking and running.

The state of the art also includes WO 2011/028114 A1, describing asports shoe having an outsole provided with a grip enhancing structureand a detector arranged for detecting movement of the shoe. The gripenhancing structure is moveable between an increased gripping state anda decreased gripping state, in that a processor is arranged to move thegrip enhancing structure between these states based on detectedmovements.

The state of the art also includes US 2012/0066938, which describes shoeoutsoles with removable and replaceable gripping pods for athletic orsport shoes. The gripping pods hold a supply of a substance thatexhibits tackiness for enhancing friction between the outsole and theany hard floor. The tackiness-enhancing substance may be time-releasedor discharged from within the shoe sole onto the lower surface(s) of theoutsole that make(s) contact with the smooth hard playing surface or maybe in response to compression or shear forces acting on the sole duringplay to prolong the tacky properties and reduce slippage.

The state of the art also includes GB 2113072 A, describing a flexiblesole for use with hiking, running, or walking shoes comprising flexibleprotrusions extending from a support portion in a direction inclinedtoward the rear of the shoe. As the shoe is pressed against the groundunder the weight of the user, the inclined protrusions flex elastically.As the protrusions flex along their length, the bottom surface of eachprotrusion in contact with the ground remains fixed relative to theground due to frictional forces. The protrusions flex by forming asmaller angle with the bottom surface of the support portion. The resultis that the support portion of the sole and the shoe attached to thesole move forward an additional distance relative to the point ofcontact between the protrusions and the ground.

The state of the art also includes WO 2008/064862 A1, describing aprofile structure for a running surface, in particular of a shoe, havingat least one profile element which is arranged or can be arranged in theregion of an associated depression on the running surface and can bepressed at least partially into the depression counter to elasticrestoring forces. When the running surface is loaded or comes intocontact with an underlying surface, the profile element is pressed atleast partially into the depression and in the process rolls on theunderlying surface by way of a rolling surface which is situated outsidethe depression. A propulsion force is generated in a propulsiondirection which is directed substantially parallel to the runningsurface or to the underlying surface.

One disadvantage with state of the art traction control devices forfootwear is that the traction control devices are active, i.e. inoperation, at all times, also when they are not needed.

The applicant has devised and embodied this invention to overcome theseshortcomings and to obtain further advantages.

SUMMARY OF THE INVENTION

The invention is set forth and characterized in the main claim, whilethe dependent claims describe other characteristics of the invention.

It is therefore provided an outsole for footwear, comprising at leastone protrusion extending from the outsole and having a portionconfigured for supporting the footwear against a ground surface,characterized by a traction-enhancing element connected to theprotrusion and selectively insertable between said portion and theground surface when the portion is at least partially supported by theground surface.

In one embodiment, the traction-enhancing element is attached to atleast a portion of the protrusion and configured for bending between afirst position and a second position; wherein the traction-enhancingelement in the second position is between said portion and the groundsurface. In one embodiment, the movement of the traction-enhancingelement between the first position and the second position is effectedby a movement of the footwear predominantly along the ground surface.

The traction-enhancing element is connected to the protrusion via anelastic connection, said connection being configured such that thetraction-enhancing element returns to the first position when it is notsubjected to external loads, the first position representing a state ofequilibrium for the traction-enhancing device.

The traction-enhancing element comprises a first side and a second side,configured such that the first side is generally not in contact with theground surface when the traction-enhancing element is in the firstposition, but is at least partially in contact with the ground surfacewhen the traction-enhancing element is in the second position.

In one embodiment, the first side comprises a friction-enhancingmaterial. The second side is generally flush with said portion when thetraction-enhancing element is in the first position. In one embodiment,the traction-enhancing element comprises a lip made of an elasticmaterial. In one embodiment, the material of the protrusion and thematerial of the lip are similar materials.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the invention will become clear fromthe following description of preferential forms of embodiment, given asnon-restrictive examples, with reference to the attached drawings,wherein:

FIG. 1 is a schematic side view of a boot having an outsole with agripping pattern in the form of a plurality of protrusions;

FIG. 2 a is plan view of an outsole having a plurality of protrusion,the figure also illustrating the traction enhancers according to theinvention;

FIG. 2 b is a sectional side view as defined by the section line A-A inFIG. 2 a;

FIGS. 3 a-c are principle sketches of a protrusion having tractionenhancers and being supported by a surface, and illustrate the functionof the traction enhancers in a static state (FIG. 3 a), upward slope(FIG. 3 b), and downward slope (FIG. 3 c), respectively;

FIG. 4 a and FIG. 4 b are schematic plan views of an outsole protrusion,illustrating two embodiments of the traction enhancer;

FIG. 5 a is a principle sketch of an outsole protrusion, being supportedby a surface, the figure showing the traction enhancers in a static,inactive, state;

FIG. 5 b shows the outsole protrusion as illustrated in FIG. 5 a, havingbeen subjected to a movement along the surface, whereby the tractionenhancer has been activated;

FIG. 6 is a sketch of an alternative embodiment of the protrusion andtraction enhancer;

FIGS. 7 a-c are principle sketches illustrating the traction enhancerswhen walking on a level surface (FIG. 7 a), a downhill slope (FIG. 7 b),and an uphill slope (FIG. 7 c), respectively;

FIGS. 8 a and 8 b illustrate various outsole patterns;

FIGS. 9 a-g illustrate various possible geometries for the tractionenhancers;

FIG. 10 a is a plan view of another variant of the invented outsole;

FIG. 10 b is a section drawing along section line CL-CL in FIG. 10 a;

FIG. 11 a is a section drawing along section line B-B in FIG. 10 a;

FIG. 11 b is a section drawing along section line C-C in FIG. 10 a;

FIG. 11 c is a section drawing along section line D-D in FIG. 10 a;

FIG. 11 d is a section drawing along section line E-E in FIG. 10 a; and

FIG. 11 e is a section drawing along section line G-G in FIG. 10 a.

DETAILED DESCRIPTION

FIG. 1 shows a boot 1 having an outsole 2, and the outsole is furnishedwith protrusions 4 that support the user's weight and provide contactwith the ground surface S. The term “outsole” generally refers to thebottom of the boot, that is, the part of the sole that comes in contactwith ground when the boot is in use. The protrusions 4 may be in theform of ridges, knobs, etc., arranged in a suitable pattern, as are wellknown in the art. Although the following description uses the term“boot”, the invention shall not be restricted to a boot, but applies toany footwear in general.

Referring now to FIGS. 2 a and 2 b, each protrusion 4 comprisestraction-enhancing elements in the form of a “lip” 6 extending aroundthe protrusion's periphery (illustrated as dotted lines in FIG. 2 a).The curved arrows in FIG. 2 b illustrate how the lips 6 may be bent downand around to the underside of the protrusion. This is also indicated inFIGS. 7 a-c. The lip is made of an elastic material (e.g. rubber,thermoplastic polyurethanes (TPU), latex, PVC or any other known outsolematerial. The lip may be molded together with the protrusion, such thatthe two form one unitary element, or the lip may be connected (e.g.glued or vulcanized) to the protrusion after the protrusion has beenmade.

FIG. 5 a, which is a schematic illustration of one protrusion 4, showshow the lower surface 7 of the lip 6 is flush with the protrusion'sground-engaging surface 8, and also how the lip has a width dimension wand a height dimension h. Typical dimensions for w and h may be in theorder of 2 mm, but the invention shall not be limited to any suchdimensions. The lip 6 comprises an upper side 12 and a lower side 13.The lower side 13 typically comprises the lower surface 7. The upperside 12 is generally not in contact with the ground surface S when thelip is inactive. However, the upper side 12 is at least partially incontact with the ground surface when the lip is bent down and under theprotrusion (FIG. 5 b).

FIGS. 4 a and 4 b illustrate two possible lip configurations: FIG. 4 ashows a plurality of discrete lip sections 6 a arranged at intervalsaround the protrusion, while FIG. 4 b indicates how one lip 6 b extendsalong each side of the protrusion. A number of conceivable lipcross-sections are shown in FIGS. 9 a-g. Various protrusion patterns areillustrated in FIGS. 8 a and 8 b.

Referring again to FIG. 5 a, this figure illustrates a walking modewhere there is no slipping between the outsole (i.e. each protrusion'sground-engaging surface 8) and the ground surface S. The static frictionbetween the ground-engaging surface 8 and the ground S maintains astationary (i.e. non-slipping) relationship between the boot and theground. In this state, the lips 6 are inactive, inasmuch as that they donot carry the weight of the user and contribute little to the staticfriction between the outsole and the surface. This is the equilibriumposition for the lip, i.e. the position which it attains when it is notsubjected to external loads or mending moments causing it to deflect.

In order for the outsole to start sliding (slipping) with respect to theground, the static friction force must be overcome by an applied force.The maximum possible friction force between the ground-engaging surfaceand the ground before the boot starts slipping is a product of thecoefficient of static friction and the normal force. This may beexpressed as:

f=μ _(s) *F _(n)

-   -   where: f=the maximum possible friction force between the        ground-engaging surface 8 and the ground S;    -   μ_(s)=the coefficient of static friction (determined by        empirically);    -   F_(n)=the normal force

The invention is based on the fact that the friction exerted by the lips6 when they are deflected and bent down, underneath the protrusion, actin a direction opposite of the movement of the boot (i.e. the outsoleand the protrusion 4). This is illustrated by FIG. 5 b. Here, theprotrusion 4 has started to slide (indicted by the arrow M), whereby thelip 6 is forced to down and fold underneath the ground-engaging surface8. The movement M is induced by a force component in the positive ornegative x-direction, and this x-force component may be due toaccelerations in the x-direction or/and an inclined surface (uphill ordownhill).

FIG. 3 a similarly illustrates a static situation on a level surface,where the lips 6 are not activated. FIGS. 3 b and 3 c illustrates adownward and an uphill slope, respectively, where the protrusion 4starts to move downwards (arrow M), thus activating the “forward” lip 6,i.e. the lip that is facing towards the direction of motion (M).

A fundamental principle behind the invention is that the lips 6 areactivated when the protrusion 4 starts to slip.

FIG. 6 illustrates a variant where the protrusion 4′ comprises a groove9. This enhances lip activation in that the groove allows for an initialrotation of the part of the protrusion where the lip is attached. Thetransition between the protrusion and the lip preferably has a radius R2to avoid stress and strain hot spots and material failure. FIG. 6 alsoshows how the lip conveniently may be furnished with an enlarged(“mushroom-shaped”) outer portion 10, and that the upper side 12 of thelip may comprise a friction material 11 which will come into contactwith ground when the lip is activated. A similar friction material 11 isindicated in FIGS. 9 e-g.

FIGS. 10 a,b and 11 a-e illustrate another variant of the inventedoutsole. A number of peripheral protrusions 4 a and central protrusions4 b are provided with respective traction-enhancing elements in the formof “lips” 6″ extending around the protrusion's periphery in a mannersimilar to that described above.

Referring specifically to FIG. 11 e, each lip 6″ comprises an upper side12 and a lower side 13. The upper side 12 is generally not in contactwith the ground surface when the lip is inactive. However, the upperside 12 is at least partially in contact with the ground surface whenthe lip is bent down and under the protrusion (FIG. 5 b). The protrusion4 a comprises a groove 9 which enhances lip activation in that thegroove allows for an initial rotation of the part of the protrusionwhere the lip is attached.

Modifications and/or additions can be made to the element as describedheretofore, but these shall remain within the field and scope of theinvention.

Although the invention has been described with reference to a protrusion4 having a rectangular cross-section, as shown in FIGS. 4 a and 4 b, itshould be understood that the invention is equally applicable toprotrusions having non-rectangular cross-sections, e.g. as shown in FIG.2. Circular, elliptical and polygonal cross-sections, etc. are otherexamples of non-rectangular cross-sections. Examples of suchcross-sections are shown in FIGS. 8 a and 8 b.

What is claimed is:
 1. An outsole for footwear, comprising at least one protrusion extending from the outsole and having a portion configured for supporting the footwear against a ground surface, wherein a traction-enhancing element connected to the protrusion and selectively insertable between said portion and the ground surface when the portion is at least partially supported by the ground surface.
 2. The outsole of claim 1, wherein the traction-enhancing element is attached to at least a portion of the protrusion and configured for bending between a first position and a second position; wherein the traction-enhancing element in the second position is between said portion and the ground surface.
 3. The outsole of claim 2, wherein the movement of the traction-enhancing element between the first position and the second position is effected by a movement of the footwear predominantly along the ground surface.
 4. The outsole of claim 1, wherein the traction-enhancing element is connected to the protrusion via an elastic connection, said connection being configured such that the traction-enhancing element returns to the first position when it is not subjected to external loads, the first position representing a state of equilibrium for the traction-enhancing device.
 5. The outsole of claim 2, wherein the traction-enhancing element comprises a first side and a second side, configured such that the first side is generally not in contact with the ground surface when the traction-enhancing element is in the first position, but is at least partially in contact with the ground surface when the traction-enhancing element is in the second position.
 6. The outsole of claim 5, wherein the first side comprises a friction-enhancing material.
 7. The outsole of claim 5, wherein the second side is generally flush with said portion when the traction-enhancing element is in the first position.
 8. The outsole of claim 1, wherein the traction-enhancing element comprises a lip made of an elastic material.
 9. The outsole of claim 8, wherein the material of the protrusion and the material of the lip are similar materials.
 10. The outsole of any one of claim 1, wherein said portion comprises a recessed portion. 